DRUGS ACTING ON THE SKIN 53 



Pustulants are drugs inducing a still higher grade of inflammation 

 when locally applied^ accompanied by migration of leukocytes from the 

 vessels into the vesicles, forming pustules. 



Caustics, or escharotics, are agents which, when locally applied, lead 

 to so great a degree of irritation that the vitality of tissues is destroyed, 

 e.g., nitric acid, caustic potash and the white-hot iron. 



Uses. — Irritants are often called counter-irritants when they are 

 used against (counter) existing irritation or inflammation by reflexly 

 causing contraction of vessels in congested or inflamed underlying parts. 

 Thus a blister on the chest leads to contraction of the vessels in the 

 inflamed pleura and relieves pleuritis. Counter-irritants are, therefore, 

 employed locally to overcome internal congestion and inflammation. 

 Rubefacients are often applied over the whole surface of the body (mus- 

 tard and turpentine) to dilate superficial vessels and equalize the circula- 

 tion in colds, chills and internal congestions. Vesicants are used to alter 

 the circulation and nutrition of adjacent parts and to secure resolution 

 and absorption of inflammatory products in joint and periosteal disorders. 

 (For details see Counter-irritants, p. 491.) 



(2) Locally contracting superficial vessels. 



Astringents are drugs which, when locally applied, make the tissues 

 drier and denser and lessen secretions. Their action is probably depen- 

 dent on various factors: partial coagulation of the albuminous fluids of 

 the tissues; coagulation of morbid secretions; removal of water; and 

 contraction of the muscular coat of the blood vessels. They are local irri- 

 tants with the exception of lead acetate and bismuth salts. The astrin- 

 gents are: 



Lead Adrenalin 



Aluminum Tannic acid, and drugs containing it 



Zinc Hydrastis 



Salts ■< Silver Cocaine 



Copper Anti pyrin 



Ferric Methylene chloride | On evapora- 



. Bismuth Ether . j tion 



Hamamelis Cold 



Ergot 

 Styptics, or hemostatics, are drugs which arrest hemorrhage, when 

 locally applied, both by coagulation of albumin of the blood and by direct 

 contraction of the vessels and tissues surrounding them. Adrenalin and 

 solutions of ferric alum, ferric chloride and subsulphate are the most 

 powerful styptics, although all astringents possess an hemostatic action. 

 Uses. — ^Astringents are employed in local loss of tone and relaxation 

 of tissues accompanied by serous, mucous or purulent exudation from 

 mucous membranes or raw surfaces. The irritating astringents are 

 usually contra-indicated in acute inflammatory conditions, but are thought 

 to prevent the out-wandering of leukocytes through the blood vessels, 

 which results in purulent exudation. 



Styptics are employed in the treatment of hemorrhage from mucous 



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